G 419 SubSurface Geology Notes PDF

Lecture Notes in Subsurface Geology Geology Department Fourth year First Semester Petroleum and Water Science Program Course code: G 419 Edited by Dr. Shaker Abo Elfotouh  Course Description, Aims...

Lecture Notes in Subsurface Geology Geology Department Fourth year First Semester Petroleum and Water Science Program Course code: G 419 Edited by Dr. Shaker Abo Elfotouh  Course Description, Aims and scope Course Description Principles and techniques of subsurface geology, including: subsurface mapping; facies and reservoir analysis; fluid-related rock properties; composition, movement and entrapment of subsurface fluids (oil, natural gas, water), and petroleum source rocks. Laboratory work emphasizes subsurface analysis of reservoirs and mapping with logs, cuttings, cross sections and subsurface maps. Applications to hydrocarbon exploration and development. Aims and scope The aim of this course is to provide the fundamental principles of common methods of subsurface exploration, with special emphasis on the application of geophysical prospecting methods to interpretation of subsurface structure in depth.  Course Outcomes Outcomes: During this course the student will develop the following: 1. Ability to plan a survey by selecting subsurface exploration prospecting techniques best suited for each case. 2. Work with maps of gravimetric and magnetic anomalies of specific areas and interpret it in geological terms. 3. Understand the role of seismic and well logging in detecting of shallow and deep subsurface structures. 4. To be able for making structural maps and 3D models of the subsurface.  Prerequisites: 1.Structural geology 2.Geophysics 3.Well logging 4.Petroleum geology 5.Sedimentology 6.Stratigraphy,…. Materials: 1. Main Textbook: Petroleum Geology eTextbook, S.L. Bend (2008) Other readings: 2. Petroleum Geology, F.K. North (1985) 3. Geology of Petroleum, 2nd edition, A.I. Levorsen (1967, reprinted 2001) 4. Applied Subsurface Geological Mapping, Tearpock and Bischke (1991) 5. Pore Geometry as Related to Carbonate Stratigraphic Traps, J.L. Stout (1964, AAPG Bull.) 6. Stratigraphic Traps in Sandstones–Exploration Techniques, Busch (1974, AAPG Mem., 21) 7. Secondary Migration and Accumulation of Hydrocarbons, W.A. England (1994, AAPG Memoir 60) Course notes handouts: 1. Porosity in carbonate rocks.; Hydrocarbon seals ; Reservoir temperatures ; Reservoir pressures ; Coalbed methane ; Shale gas Software: Surfer Program contouring package (provided in the computer lab)  CONTENTS 1. Surface Geology 2. Subsurface Geology 3. Importance of subsurface geology 4. Well measurements: 5. Well samples: Well Cutting, Coring, Fluids, etc. 6. Subsurface maps 7. Well correlations 8. Cross sections 9. 3D diagrams  Surface Geology There are several areas to look for oil. The first is the observable, on the surface of the ground. Oil and gas seeps are where the petroleum has migrated from its source through either porous beds, faults or springs and appears at the surface. Locating seeps at the surface was the primary method of exploration in the late 1800’s and before.  Subsurface Geology One of the most valuable reasons for learning about the subsurface is understanding the materials below man-made structures (constructions). The subsurface data also contain the locations and information for oil and gas wells, geothermal wells, water wells and geotechnical borings (geotechnical engineering and construction).  Subsurface Geology Subsurface geology is the study of the physical properties and location of rock and soil found below the ground surface. In case of shallow depths, these studies are commonly called geotechnical reports which are critical for building structures safely in areas with geologic hazards, and, also, for groundwater exploration. In case of deep depths, these studies are called exploration reports and are necessary for petroleum prospecting and development. Subsurface Geologists use different types of subsurface data to: – produce and develop variety of resource maps, – make the subsurface interpretation of geologic maps, – better understand faults, folds and other structures features – produce 3D models of the geological setting in an area. – etc …  Importance of Subsurface Geology Petroleum exploration: The usefulness of subsurface geological methods in petroleum exploration and production problems has increased steadily since the beginning of the petroleum industry. As more subsurface understanding is called for, more and more geologists become specialized in this type of work, until in many areas practically all of the exploration geology is based on subsurface interpretations.  Importance of Subsurface Geology Groundwater Subsurface studies are very important for understanding and protecting groundwater aquifers in order to maintain a steady supply of suitable water. These studies help us to understand how water flows, through and is stored in aquifers as well as how contaminants may enter an aquifer. This allows people to plan future development so that aquifers remain viable for years to come.  Importance of Subsurface Geology Engineering: The construction industry depends heavily on mining sand and gravel resources. These resources provide the raw materials needed to produce concrete and asphalt for our roads, offices, and homes. Understanding the amount and quality of the sand and gravel in a resource deposit can influence many decisions in the mining process. Total reserve estimates, mine design, and mining method all depend on having quality subsurface data.  Importance of Subsurface Geology Environment: The subsurface studies can reveal hazards such as underground coal mine workings and unstable slopes. It is significantly cheaper to design for hazards than to repair the damage later. Thus, engineering companies often obtain geotechnical reports before starting any major project. Others: Subsurface studies can also provide critical inputs for imaging magma chambers, geothermal exploration, locating active faults (paleo-seismology), and metal mining.  HOW IS SUBSURFACE INFORMATION COLLECTED? There are several methods available to collect subsurface information. There are depth and resolution limitations associated with each method. Thus, knowledge of the limitations of each method is critical in undertaking a subsurface survey. 1. Boreholes Drilling boreholes is the primary way used to obtain subsurface information. Drilling brings rock to the surface for direct study, which are described on site and may be sent to a laboratory for additional study. Tests can also be performed within open boreholes, to better understand the materials in place Information obtained from drilling includes material properties, changing rock or soil type, fault locations, and depth to water or bedrock. A geological cross-section (AA) extending from west Assiut area (west) to Red Sea Hills (east)  HOW IS SUBSURFACE INFORMATION COLLECTED? 2. Seismic surveys Seismic surveys relies on analysis of seismic waves refracted or reflected from subsurface layers. Seismic surveys are categorized as either active or passive. In active seismic, the geophysicist creates a seismic wave by hitting the ground with a hammer or using an air-gun, In rare cases, small explosive detonations may be used to create a seismic signal. In passive seismic, uses naturally occurring waves or the “background noise” as the seismic source. Seismic surveys can be conducted on land or in the water-the effective depth of the survey may vary from tens of feet to several kilometers. All active seismic surveys, involve sound waves generated from a sources that travel through the ground, are refracted, and are then received by detectors. The speed at which the waves travel tells us a lot about what layers are made of and how they are arranged. 3. Gravity and magnetics They are often work hand-in-hand to characterize the subsurface. Gravity surveys identify density differences in rock formations. This is useful for identifying the depth of bedrock under unconsolidated sediment and depth to basement rocks under sedimentary basins. Gravity surveys can also locate contacts between two distinct densities of rock at depth. Magnetic surveys identify magnetic contrasts in rocks. This is useful for mapping faults, folds, and rocks with more magnetic minerals. Both surveys can be conducted on the ground for high-resolution data. They can also be run from an airplane for lower resolution and greater coverage. These surveys are generally faster and cheaper to acquire than other data types. However, interpreting the data requires more training and is seldom used independently. Residual and regional separation of potential data  HOW IS SUBSURFACE INFORMATION COLLECTED? 4. Ground penetrating radar Ground penetrating radar (GPR) is a method of imaging the subsurface using radar pulses. At an airport, for instance, a radio tower will emit a radio wave that bounces off an aircraft and returns to the detector, informing an air- traffic controller of the aircraft’s location. The same concept applies if the radar wave is pointed down toward the earth. The radio wave travels through the subsurface and bounces off of soil and rock layers. Faults, contacts between different rock types, and discrete objects like boulders or voids are then visible. GPR has a variety of effective depths (generally